>> we see, they call it skinny fat, i see, right, people who look skinny but then they have large waists. >> not even just large waists. they can have normal waists. jimmy bell, a neuro imageer at cambridge, university of college london calls it tofi, t-o-f-i. thin on the outside, fat on the inside. when you do mris inside, you can actually see the fat in all of the organs. the muscle, the heart, et cetera. bottom line is, from your weight, you can't tell where you are. >> so how -- so what do you do? how can you tell, first of all? >> well, in fact, the best way is, again, waist circumference. that's the cheapest way. there are some lab tests your doctor can do, a fasting insulin and some liver function tests that can give you clues as to whether or not there is a problem or not. but the single best way to deal with excess fat is to get it off and the easiest way to do that is to exercise. the problem with exercise is, every doctor will tell you, if you exercise, you would lose weight. that's because they say a calorie is a calorie.